OCZ Power Stream 470

For a complete rundown of testing equipment and procedures, please refer to the article SPCR's Revised PSU Testing System. It is a close simulation of a moderate airflow mid-tower PC.

In the test rig, the ambient temperature of the PSU varies proportionately with its actual output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a precise high power load tester which allows incremental load testing all the way to full power for any non-industrial PC power supply. Both fan noise and voltage are measured at various loads. It is, in general, a very demanding test, as the operating temperature of the PSU reaches 40°C or more at full power. This is impossible to achieve with an open test bench setup.

The testing was conducted in the "sound lab", a 20' x 10' x 8'(ceiling) carpeted den with heavy drapes across windows on one of the short walls. Acoustics are well damped.

Ambient conditions during testing were 23°C and 15 dBA, with input of 119VAC / 60 Hz measured at the AC outlet.

OCZ-470ADJ 470W PSU

DC Output (W)

65

90

150

200

250

300

400

470

AC Input (W)

93

123

197

252

314

373

510

599

Efficiency

70%

73%

76%

79%

80%

80%

78%

78%

Intake Temp (°C)

27

28

32

35

38

42

46

48

PSU Exhaust (°C)

31

32

38

42

47

52

59

61

Fan Voltage

5.6

5.6

5.7

5.7

5.7

5.8

7.5

7.9

Noise (dBA/1m)

27

27

28

30

32

32

36

38

NOTE: The ambient room temperature during testing varies a few degrees from review to review. Please take this into account when comparing PSU test data.

¬†

Red means voltage is more than 5% high.

Yellow means voltage is more than 5% low.

1. VOLTAGE REGULATION was very good, but subject to careful setting of the voltage trim pots on the back panel. The adjustment range is as follows:

+12V: 10.7 ~ 13.3V

+5V: 4.5 ~ 5.6V

+3.3V: 2.8 ~ 3.8V

For the 12V and 5V lines the adjustment range is up or down 10%, while for the 3.3V line, it is even bigger, ~15% up or down. The range of adjustment provided is quite large, probably too large for safety, in my opinion. Especially when voltage is set too high, the life of components can be seriously shortened. Also, trim pots change value with temperature and age.

But the LED indicators help to avoid problems. The voltage adjustment is made with a small screwdriver. A plastic sticker over the trim post must be removed first. When the voltage falls within the +,-5% range, the LED directly below the trim pot glows green. Above that, it glows red; below that, it glows yellow.

Tested against a fairly accurate multimeter, the LEDs generally glowed green within +,-5% of the target voltage. This seems too loose a tolerance. When the 12V LED is green it could be 11.4V or 12.6V. A 2% range for green would have been more useful, especially for the performance oriented user interested in such adjustments. I'd recommend using a multimeter at the terminals of an unused output connector to tweak the voltages instead. This should be done while the computer is running. Naturally, care must be taken to avoid shorts.

When set for perfect accuracy at 90W output, the voltages sagged slightly as output increased, but it was well within the 5% range.

Output

12V

5V

3.3V

The voltages were calibrated at the 90W output level. Ideally they should be calibrated at about the median load of the PC it will be used with.

90W

12.0

5.00

3.30

400W

11.82

4.91

3.17

2. AC-to-DC Conversion EFFICIENCY was very good. It reached a high of 80% at 250W and 300W. Efficiency at lower power is less than that of the other efficiency leaders among SPCR tested PSUs (Seasonic Super and Enermax Noisetakerseries) but still good. Keep in mind that even the most power-hungry single-CPU system is not likely to draw much more than 200W (DC) under max load so unless you have a multi-CPU workstation, the efficiency with this PSU in your system will usually be in the <80% range.

3. POWER OUTPUT: The unit ran with good stability at all output levels. At the full 470W output, the test was limited to a cautionary 3 minutes instead of the 15~20 minutes at most of the other power levels because of the high AC current draw and the high exhaust temperature.

4. POWER FACTOR was measured at about 0.63 at the minimum test power level to 0.71 at the highest. This is mediocre. It's likely that the OCZ-470ADJ has no PFC or passive PFC.

5. FAN VOLTAGE: It started somewhere above 5V and stabilized at ~5.6V with 65W power output. The fan fans ramp up in voltage less than any other PSU tested thus far. Even at 470W and an intake air temperature of 48°C, the voltage to the fans never exceeded 8V. Perhaps the designers calculated that with the increased pressure of the 2 fans in push-pull mode, this is all the voltage needed for adequate airflow. Only when the output reached above 300W and the intake air temperature exceeded 40°C did the fan voltage exceed 6V. Strangely, even though the monitored fan voltage did not rise, the noise did gradually rise as power output increased. It is possible that the intake fan is running at a higher voltage or perhaps is a faster fan. There was no time to investigate this fully.

6. NOISE was measured at 1 meter from the exhaust grill, with both the SLM and the PSU at least 1 meter from walls. All other noise sources (including the fans in the PSU load tester) were turned off during measurements and listening.

Subjectively, the OCZ-470ADJ is quiet at startup and does not get much louder to quite a high power output and temperature. It does not pose a real challenge to the quietest SPCR Recommended PSUs, but it stays at quite a modest volume to very high operating temperature and power output. The noise maximum of 38 dBA/1m is not bad considering the 470W power output.

The fan has some buzzing or humming noise at low speed, as well as a bit of chatter. This noise gets obscured somewhat beneath the whoosh of wind turbulence as the fan speeds up. There was no high frequency whine from the electronics in this sample. (Coil noise is often the result of interactions between components, however, so the absence of this noise in the lab does not ensure its absence when the PSU is connected to various combinations of PC components.)

A CAUTION: The noise-to-power performance achieved here is specific to prevailing test temperatures and conditions. The test noise results represent performance with a real PC in a reasonably well-optimized "silent" case.